1980 Datsun 720 turbodiesel

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plenzen
Posts: 868
Joined: 13 years ago
Location: Cochrane Alberta Canada

Re: 1980 Datsun 720 turbodiesel

#16

Post by plenzen » 4 years ago

Pretty sure on my 25 to advance the timing I roll it towards the engine. A "quieter smoother, freer" idle will denote retarded timing while one that's a bit noisier will denote advanced. Too retarded will make for difficult starting
Have you returned the smoke screw to the pump and wound it in ? With you saying the governor allows the engine to spin up to 3000+ rpm this still sounds like fuel problem to me.
Retired Pauly
Problem with being retired is that you never get a day off.
1987 D21-J SD25 KC
KJLGD21FN

waynosworld
Posts: 517
Joined: 7 years ago
Location: Vancouver Washington USA

Re: 1980 Datsun 720 turbodiesel

#17

Post by waynosworld » 4 years ago

plenzen wrote:Pretty sure on my 25 to advance the timing I roll it towards the engine. A "quieter smoother, freer" idle will denote retarded timing while one that's a bit noisier will denote advanced. Too retarded will make for difficult starting
Have you returned the smoke screw to the pump and wound it in ? With you saying the governor allows the engine to spin up to 3000+ rpm this still sounds like fuel problem to me.

I noticed a little bit of black smoke when I revved it today, the smog/smoke screw has been removed, never seen black smoke since I changed it till after removing that screw.
This engine starts easy and is very quiet compared to my other engine, my other 521 engine is very noisy and when it is cold out it is hard to get going, but once going, it is the better running engine, maybe I should say it is noisy only at an idle.
I will change the timing of the 720 pump tomorrow, if nothing changes I can put it back, I have done it before, I need to keep trying to make it run better, it runs alright now, but I would like a better RPM range.

Let me put it another way, my 521 with 350 gears in the rear will get to almost 20mph in first, the 720 with 330 gears in the rear will only go about 15mph in first, it has better gearing but will not go as fast even with a turbocharger, it's the same in every gear.
I know the voices are not real,
but they have some really good ideas.

waynosworld
Posts: 517
Joined: 7 years ago
Location: Vancouver Washington USA

Re: 1980 Datsun 720 turbodiesel

#18

Post by waynosworld » 4 years ago

OK, I changed the pump timing a little, I really cannot tell if it made a difference or not to tell the truth.
I did take it on the hiway, and did a sort of test, my speedo is off, it's supposed to have a 389 geared rearend, but it has a 330 geared rearend, so I am going faster that the speedo shows, I did get it to show a little over 60mph on the speedo.
So here is an observation, while going down the freeway I can get it to 2300rpms fairly easy, but then it starts getting tough, I pushed it to the max to see what would happen, I floored it and everything after 2500rpms was slow to gain, and it topped out at 2680rpms, I could let up on the pedal and it would hold that rpm, 6psi of boost or 9psi of boost made no difference 2680rpms was it, it would go no faster in 5th gear.
So on the neighborhood streets I did another test, in first or second if I gave it the pedal, I could get over 3000rpms, but it didn't want to go there, everything after 2500rpms was forced and I actually didn't like the sound of it either, it just sounded over revved, but as I said in past replies, I don't even rev up my other 521 SD25 engine that high in them gears either, I probably shift at 2500rpms in first, second, and maybe third, then I will rev it higher in forth and fifth, mostly just 5th on the hiway, fifth is 80mph at 3000rpms.
So, Larry modified the turbocharger when he built this system, he took it to work and machined out the compressor side to except a larger compressor vane, he did this to build more boost at lower rpms, he told me it took him all day to do it, could this be my issue, could it be getting to much air, or could the compressor side be cavitating?
Now understand this, it acted the same way when I first bought it, so I don't believe it has anything to do with where the throttle body is, it has been both ways and acted the same both ways, the big difference is that before the EGTs would be running at 1400 degrees and trying to go higher, now they were running at 900 to a 1000 degrees floored at 2680rpms.
I do have two stock turbochargers, they are not stock to this application if there is such a thing, but they are un-modified, but before changing the turbocharger out which will likely be a big job, I want to know that this is the issue, I want to know that the vane is to big for the hole it is in.
I know the voices are not real,
but they have some really good ideas.

plenzen
Posts: 868
Joined: 13 years ago
Location: Cochrane Alberta Canada

Re: 1980 Datsun 720 turbodiesel

#19

Post by plenzen » 4 years ago

Really hate to sound like a broken record but I still think it's running out of fuel.
Fuel equals heat, you used to have it, now you don't. The engine requires more fuel for a higher load. 1st or 2nd gear and WOT is very light load. 5th gear on highway WOT is a heavy load. It needs more fuel at that speed. WOT in neutral requires very little fuel that's why it will spin up to 3000 + rpm.
Retired Pauly
Problem with being retired is that you never get a day off.
1987 D21-J SD25 KC
KJLGD21FN

waynosworld
Posts: 517
Joined: 7 years ago
Location: Vancouver Washington USA

Re: 1980 Datsun 720 turbodiesel

#20

Post by waynosworld » 4 years ago

plenzen wrote:Really hate to sound like a broken record but I still think it's running out of fuel.
Fuel equals heat, you used to have it, now you don't. The engine requires more fuel for a higher load. 1st or 2nd gear and WOT is very light load. 5th gear on highway WOT is a heavy load. It needs more fuel at that speed. WOT in neutral requires very little fuel that's why it will spin up to 3000 + rpm.
Well I don't know if this would mean anything or not, but I opened up the propane injection just now and took it on the freeway, it has an electrical cut off switch, I flipped the switch a couple times and felt no difference, and I know it was injecting propane because the needle was dropping, as when I let off the pedal it would come back, it is a vacuum feed, no vacuum it doesn't feed propane into the system, I think it was working but maybe it wasn't feeding enough propane into the engine, the vacuum sensor is in front of the turbo on the airfilter, so it works the same as when Larry set it up.

How would I go about making an inline injection pump richer?
I know the voices are not real,
but they have some really good ideas.

plenzen
Posts: 868
Joined: 13 years ago
Location: Cochrane Alberta Canada

Re: 1980 Datsun 720 turbodiesel

#21

Post by plenzen » 4 years ago

Put the smoke screw back in and wind it in.
In is more fuel, out is less.
Retired Pauly
Problem with being retired is that you never get a day off.
1987 D21-J SD25 KC
KJLGD21FN

waynosworld
Posts: 517
Joined: 7 years ago
Location: Vancouver Washington USA

Re: 1980 Datsun 720 turbodiesel

#22

Post by waynosworld » 4 years ago

plenzen wrote:Put the smoke screw back in and wind it in.
In is more fuel, out is less.
Would you agree that the arm in the start position would be in the richest position?
I know the voices are not real,
but they have some really good ideas.

plenzen
Posts: 868
Joined: 13 years ago
Location: Cochrane Alberta Canada

Re: 1980 Datsun 720 turbodiesel

#23

Post by plenzen » 4 years ago

The arm position I don't believe denotes how much the fuel delivery adjustment inside the pump.
The screw allows more fuel to flow at a given rack position.
The external lever merely moves the rack it does not determine how much fuel is being delivered at a given position.
I'm trying to think of an analogy to explain this. You have to quit thinking gasoline engine. Rich and lean are gasoline terms. Diesel is different.
Retired Pauly
Problem with being retired is that you never get a day off.
1987 D21-J SD25 KC
KJLGD21FN

waynosworld
Posts: 517
Joined: 7 years ago
Location: Vancouver Washington USA

Re: 1980 Datsun 720 turbodiesel

#24

Post by waynosworld » 4 years ago

plenzen wrote:The arm position I don't believe denotes how much the fuel delivery adjustment inside the pump.
It allows more fuel to flow at a given rack position.

Well then I don't know how to explain this other than to say I have an injection pump pulled half way apart, when I look at the diaphragm I see that the rack is pulled by vacuum towards the rear, the spring in there is always trying to force it towards forward towards full throttle, so when there is no vacuum in the venturi the injection pump rack is at full throttle.
The smoke/smog screw forces the rack towards the idle position, the farther it is screwed in forward towards the arm forcing the top of the arm backwards, the closer it gets to the fuel cutoff position, since mine has been removed. it is as far away from the fuel cutoff position as it can get which says to me it is richer, I never seen black smoke come out the tail pipe the way I have it set up till I removed the smoke/smog screw, it's not much black smoke, but enough to see when I revved it yesterday.
The way I see it, the farther the smoke/smog screw is turned in, the leaner it is, the farther the screw is turned out towards the oil filter, the richer it is, since mine is removed, it is as rich as it is going to get concerning that screw.

Now that doesn't mean that the vacuum created by the throttle body is letting the rack move to the rich position, maybe I have to much vacuum because of the turbocharger being to close to the throttle body and that venturi is creating vacuum when it is not supposed to.
I know the voices are not real,
but they have some really good ideas.

waynosworld
Posts: 517
Joined: 7 years ago
Location: Vancouver Washington USA

Re: 1980 Datsun 720 turbodiesel

#25

Post by waynosworld » 4 years ago

OK, so I was standing there looking at my engine bay trying to figure out what I can make to fix the vacuum issue that still exists, but it isn't as big of an issue as it was, it was 10psi vacuum, now it is 1 or 2psi unless I am in first or second and under compression, then it goes to 5 briefly, I am looking at all my vacuum or pressure hoses when I look at the only hose/line that I don't have connected, it's the one that comes from the injection pump that is supposed to be connected to the fitting on the throttle body cover that goes to the air filter from the throttle body in stock configuration, I cannot use that fitting anymore because it is under boost a lot which would try to force the injection pump diaphragm and rack to the idle position.
So I am wondering where to put this line when it dawned on me that if this hose were to go to the air filter itself two things would happen, one is that it would be filtered air going in and out like the stock configuration, and the other thing that occurred to me was that it would actually have a slight vacuum because of the turbocharger sucking air from in there, especially at higher rpms, the dirtier the air filter, the more vacuum, the more it would help pull the diaphragm/rack to a richer position.
So I pulled the propane injection hose off the air filter fitting as the propane is turned off anyway(tank valve is closed), and I connected that injection pump line to the air filter fitting, then I started it up, it ran normal, so I took it for a drive, on the freeway I noticed something right away, the wall I keep harping about was much softer, it doesn't go any faster, but it is a smoother transition, it doesn't get to a certain rpm and fall on its face now, before I used the top third of the pedal and when I came to the wall I had to just put my foot in it to get to higher rpms, now I am using more of the pedal/deeper into the pedal to get to the same rpms, I suspect I would get better freeway fuel mileage if I disconnect this line.
Another thing I noticed was that the EGTs were running a little hotter, it's the first time I have seen it above 1200 degrees since I changed things, but I was floored when it happened, I was trying to get up to top speed on the freeway.
When I returned home I pulled the line off the air filter to see what would happen and noticed an rpm change, at idle the rpms were higher when I disconnected this line, and they lowered when I connected it, I don't know what this means for sure, as I don't have gauges on these lines telling me what it is going on in each line at different rpms.
I am making this up as I go, it runs real good considering what I have done over the last few days, all in all I consider this a positive result so far, wait till you see what I have in mind to fix the vacuum issue, if it works you will likely laugh.
I know the voices are not real,
but they have some really good ideas.

waynosworld
Posts: 517
Joined: 7 years ago
Location: Vancouver Washington USA

Re: 1980 Datsun 720 turbodiesel

#26

Post by waynosworld » 4 years ago

So today I made a valve of sorts, it didn't work as good as I was hoping, it did work, just not as good as the valve I have been using which only works OK.
Here are the valve parts.
Image
Here it is without the spring installed.
Image
Here it is with the spring installed.
Image
Here it is put together.
Image
And here is the tube I mounted it to, I removed the blow off valve and mounted it.
Image
The reason I made this was to test if I could get rid of all the vacuum in the system when I let off the pedal and am under compression in first, second, and third, fourth and fifth are not an issue, I don't know why.
What happened with this valve was that the ping pong ball was just a little to big for the tube it is in, the vacuum from the engine pulled the ball all the way to the "T" and it tried blocking that hole, it is real close top that hole, to close.
It did work though, the moment I pushed on the pedal it went back to where it was supposed to go and allowed the turbocharger to build up 10psi boost, but when I let off, it would build 5psi of vacuum, the valve I have now only has 2 or 3psi vacuum, my goal is for 1psi vacuum.
I have put together another valve using the next size larger fittings, but I didn't have the parts to complete it, I will buy them tomorrow, this one has more room on the sides of the ball to let the air past so the ball doesn't get sucked all the way to the outlet even though it is still close.
Image
Image
This is just a temporary valve, if I can get one to work the way I want it to work, I will make one out of metal tubing and a hollow metal ball, it will also likely be a straight tube instead of a Tee, I just want to see if I can do it.
The truck runs alright now other than the slight vacuum issue, I also need to find the correct speedo drive gear so I can tell how fast I am really driving down the freeway instead of guessing, I might be going over 80mph, but I cannot tell as I normally drive a 521, this 720 is longer and heavier.
I know the voices are not real,
but they have some really good ideas.

waynosworld
Posts: 517
Joined: 7 years ago
Location: Vancouver Washington USA

Re: 1980 Datsun 720 turbodiesel

#27

Post by waynosworld » 4 years ago

I fueled up the truck today, while I was there a couple guys from the auto collision center/auto shop next door came over asking what engine I had, when I told them they said they could tell it had something strange in it from the sound, so I showed it to them, I explained what I had done and the issue I was having, they listened and then made a comment, they said all turbodiesels have oil in the intake system, they had never taken one apart that didn't, even the new ones, is this true, are all turbodiesel intake systems coated with oil?
I made another valve today, this one worked quite well except the vacuum was a little higher than what I am using already, but it is what I came up with, it needs some adjusting and I will try it again tomorrow, the spring was just a little to tight, I made an adjustment tonight, I released about a half inch tension which is about 15/20 percent of the total tension.
Here are the parts.
Image
Here it is put together.
Image
I also went to the local turbo specialists(extreme turbo systems) and picked their brains a little, the guy thought it was cool, but said that they did gas turbos and then the guy suggested a power brake booster check valve, and if that didn't work try out the local industrial hose and tubes place for bigger check valves, I didn't show him my first attempt at a valve, I came up with this after I talked to him, the industrial place wasn't open(out to lunch), and they would not be back for over an hour, the guy standing there wasn't happy when I pointed out the little clock sign that showed 2:30 as it was just after 1pm, he got in his Jeep and drove off, I was right behind him.
I know the voices are not real,
but they have some really good ideas.

waynosworld
Posts: 517
Joined: 7 years ago
Location: Vancouver Washington USA

Re: 1980 Datsun 720 turbodiesel

#28

Post by waynosworld » 4 years ago

So after making that slight modification last night I installed it this morning and went to the wrecking yard to look at brake booster check valves, I brought 3 different types home, I will make a plate and install them to see if any will work better than what I made.
Fact is this last one works great so far, on the way to the wrecking yard I had to keep letting off the pedal because I was going over 10psi boost, on the way home I adjusted the waste gate and did it perfect the first time, if I floor the pedal it creeps up to 10psi and goes no farther now, but when I let off it still gets to 4psi vacuum, but it is quiet the way it is now, so I will start to fine tune what I have made now, what I am trying to do is not have the ball open at an idle, but open during any other higher vacuum situation, I will loosen the valve a sixteenth inch at a time now until I get where I want, or till I go to far, then I will add a washer, this one works good so far.
I don't like hearing the boost blow off, and now that the waste gate is functioning I don't have to hear it anymore, so this is better than that $200.00 valve I bought.
Here is the valve installed.
Image
Image
I know the voices are not real,
but they have some really good ideas.

waynosworld
Posts: 517
Joined: 7 years ago
Location: Vancouver Washington USA

Re: 1980 Datsun 720 turbodiesel

#29

Post by waynosworld » 4 years ago

I tried the biggest power brake booster check valve this afternoon, it's not near big enough, it creates more vacuum and is open all the time, even at idle it is drawing air, it didn't mess the idle up much, but under compression/deceleration the vacuum is back above 5psi and it stays there, while the one I made is at 1/2psi vacuum most the time under the same conditions and does spike to 4psi only briefly.
I cut over a half inch out of my adjuster loosening the spring holding the ping pong ball in place, but it really has not changed anything much, and I have met my limit, as if I even rev the engine even a little it draws in air on that brief rpm drop, so now the only thing I can think of to do is put an o-ring in there where the ball seals to make that seal softer on the ball than resting on the 90 degree edge of PVC which eventually will ruin the ball, I will be carrying a spare ball, no tools needed to change it either.
Once I feel this is going to work long term, I will make another one out of metal that I hope will be even shorter.

I now want to know my fuel mileage, and so I need to find the proper speedo gear to get that correct.
It runs great, it still don't like going over 2500rpms, but I can get used to it as it is going plenty fast at 2500rpms in fifth gear.
I know the voices are not real,
but they have some really good ideas.

waynosworld
Posts: 517
Joined: 7 years ago
Location: Vancouver Washington USA

Re: 1980 Datsun 720 turbodiesel

#30

Post by waynosworld » 4 years ago

OK, I sent this message to Larry a week ago, I have been going thru my messages to see if I missed anything.
__________________________________________________________________________________________________________
My message to Larry,

Hello Larry, I have a few questions for you, first one would be is this a forklift injection pump with a governor that is set somewhere around 2600rpms or did you have it set that low?
The second question is did you have the injection pump modified internally or did you just set it/adjust it with the smoke/smog screw?
Did you change the pump timing from stock?
I actually have this running pretty good now, no EGT temp issues at all now and I don't even have the inter-cooler hooked up anymore, I have not seen 1200 degrees since I changed it, I kinda wish I had not cut the front of my truck up to install it now.
I had to change stuff though, but I am now hitting a wall, it acts like the governor is kicking in while a stock automotive injection pump governor is set at 4000rpms, so I need to know if it is a governor I am fighting.
Right now I am hitting 7 or 8psi on the hiway when accelerating, I can hear it blowing off, and I even had to remove the smoke/smog screw to get more fuel, that alone made a noticeable difference and it still don't blow black smoke like it used to.
I have not used the propane since changing it, I will have to think about it a while, I believe it will work the same as it did before, but right now I am just trying to get the engine sorted out, then I will worry about the propane injection.
Please get back to me about the injection pump, I really need to know. wayne
___________________________________________________________________________________________________________
I received this in reply from Larry

It's the original pump from that engine. 83 720. Delivery valves have been adjusted to deliver more fuel. Governor spring has been tighten so that it does not defuel so early. Seems like something is wrong with your new set up and that it is not allowing the diaphragm to pull the rack full open. I have a feeling that you took the hose clamp off the vacuum hose right before the throttle body. That hose clamp controls the amount of boost the diaphragm sees and that controls the fuel....and exhaust gas temp. If you removed the clamp, the diaphragm sees any boost, it will keep adding fuel for high egt.
___________________________________________________________________________________________________________

Now this is not even close to what he put together now, the hose clamp on the vacuum hose means nothing anymore as that system is history, but what interests me is the comments about the delivery valves and the governor being tightened, does anyone on here know exactly what he did to the delivery valves, are they adjustable and how did he do it?
And the governor, does tightening it mean he turned the screw into the housing, or out of the housing?
Does anyone know what this means? "Governor spring has been tighten so that it does not defuel so early"
I know the voices are not real,
but they have some really good ideas.

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